As energy, fuel, and transportation costs continue to rise along with concerns about greenhouse gas emissions, it is desirable to integrate power generation systems into the devices for which the electricity is generated. Hybrid automobiles, for instance, generate electricity through regenerative braking, which converts the kinetic energy of the vehicle to electricity as it slows. This electricity is then used to power the car, reducing its fuel consumption and increasing its energy efficiency, thus lowering travel costs. Conceptually similar systems are viable for other forms of transportation and even for standalone power production and would allow for reduced oil consumption and carbon dioxide emission.
Combined cycles have already been used in electric power generation to optimize efficiency. In a combined cycle, the exhaust from a first thermodynamic cycle, referred to as the “top cycle”, is used as the heat source for a second cycle, called the “bottom cycle”. This allows more useful work to be extracted from a fixed quantity of fuel, increasing efficiency. In a non-combined cycle, the exhaust heat is usually wasted. The increased fuel efficiency of the combined cycle lowers the costs of both fuel and energy—all while reducing emissions.
The integration of a combined cycle into a hybrid vehicle could thus greatly enhance the energy efficiency of such vehicles and reduce petroleum-based fuel consumption. The implementation of a combined cycle to create hybrid airplanes is especially significant, as the ambient temperature in which it cruises is significantly cold, creating a high delta Temperature. Though an enormous increase in air travel is predicted over the next few decades, such a system would help to partially negate its environmental impact.
Thus, the need exists for a system to increase fuel efficiency applicable in a wide variety of situations, providing both environmental and economic advantages.